Stabilizing clay soil with hydroxy-aluminum solution

ABSTRACT

A method of stabilizing clay soil comprising admixing the clay soil with an effective amount of a solution of hydroxy-aluminum having a concentration of at least 4 molar.

RELATED APPLICATIONS

This application is related to applications Ser. No. 281,799, by MARIONG. REED et al; Ser. Nos. 281,751 and 281,752, both by TOR LOKEN et al;all filed on July 9, 1981.

BACKGROUND OF THE INVENTION

Many clay deposits often need to be stabilized before they can carry anyadditional load such as is applied during filling and concentrationactivities. This is specially true for the so-called quick clays whichfrequently are found, for example, in northern Soviet Union,Scandinavia, Canada, upper New York State, and New Zealand. Clays wereoriginally deposited in marine and brackish water in a short periodafter the last glaciation, and later during the continental (isostatic)uplift were raised above sea level. However, only certain of these claydeposits were subsequently changed into sensitive quick clays. Twoprocesses are mainly responsible for such a change. The original porewater salt content of the clay may have been leached by percolatingground water, or organic matter from logs or marshes which will act asdispersing agents may have been introduced into the clay. The firstprocess has been most important in clays found in Norway, while quickclays containing high organic content formed by the second process arefrequently found in Sweden and Canada.

The quick clays will in the undisturbed state exhibit a certain limitedstrength, but will upon remoulding completely liquefy. This samephenomena has caused several quick clay slides in the lowlands ofeastern and middle Norway, often with catastrophic consequences.Heretofore, several chemical stabilization schemes have been tried forsuch clays. Among them were aluminum chloride (AlCl₃) and potassiumchloride (KCl). The quick clays have been stabilized in two ways. Theclay can be mixed and remoulded with the chemicals, or the chemicals canbe allowed to diffuse into the undisturbed quick clay. The disadvantageof the salt diffusion method is the long time it takes to reach therequired penetration. The diffusion method has been applied only once,so far as is known, in full scale in the field, when salt wellscontaining KCl were installed two years prior to a major highwayconstruction.

Heretofore, a method for deep stabilization with unslacked lime (CaO)was developed. Lime is an old stabilizing agent that has been usedoccasionally. In China it was used centuries ago as a constructionmaterial. In the U.S.A. in the 1940's and Europe in the 1950's lime wasused as a surface stabilizing agent. The deep stabilization methodinvolves mixing and molding the lime with the clay to form a series ofpiles which extend down into the clay. These piles provide lateralstabilization to the clay deposit.

Both the lime and potassium chloride methods have some disadvantages.KCl will stabilize the undisturbed circumjacent clay, but not thedisturbed clay. Furthermore, CaO makes an unhomogenous stabilization.Pockets of lime cause brittle cylinders with small sideways shearstrength. In addition, CaO is not useful on clays with high watercontent. While hydroxy-aluminum as Al(OH)₂.5 Cl₀.5 has not been used asa clay stabilizing agent in foundation engineering before it has beenapplied as a cementing agent in preparing desired clay microstructuresfor laboratory studies. Hydroxy-aluminum and potassium chloride havealso been used in wells to treat water sensitive clay containingformations and to provide sand stabilization. Relatively dilutesolutions and overflushes are used in the field. These methods aredisclosed in U.S. Pat. No. 3,603,399 issued Sept. 7, 1971 and U.S. Pat.No. 3,827,495 issued Aug. 6, 1974 both to Marion G. Reed as assignor toChevron Research Company.

In summary, there is still need for a method of stabilizing clay soilwith chemicals that provides lasting and effective stabilization forclay deposits.

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENT INVENTION

The present invention provides for stabilizing clay soil by admixing aneffective amount of hydroxy-aluminum solution having a concentration ofat least 4 molar with the clay. The admixture is preferably done in amanner so that the stabilized clay forms a series of piles which extendinto the clay deposit at spaced apart location to provide stability forthe entire clay containing deposit. The desired size, location andnumber of the piles are determined. An effective amount ofhydroxy-aluminum solution having a concentration of at least 4 molar isadmixed with the clay in place in each location in the deposit to reactwith the clay and thereby form the desired piles.

An effective amount of hydroxy-aluminum solution means that enoughhydroxy-aluminum is present in the solution to saturate the clay and togel the water in the clay and added to the clay by the solution. Thisusually requires that at least 5 ml of at least 4 molar concentrationhydroxy-aluminum solution per 100 grams clay soil wet weight to get somebenefits of the present invention. In some clays less solution mayachieve the desired results.

Typically, the size, i.e. the volume of a desired pile to be formed inthe clay containing deposit, is determined and the wet weight of theclay soil within such pile is determined. A hydroxy-aluminum solution atleast 4 molar concentration is formed. It is generally preferred thatthe concentration hydroxy-aluminum solution be at least 6 molar andpreferably higher. An effective amount of the hydroxy-aluminum solutionis admixed with the clay.

OBJECTS OF THE INVENTION

It is a particular object of the present invention to provde a method ofstabilizing a clay containing deposit by admixing with selected portionsof the clay soil in the deposit on an effective amount ofhydroxy-aluminum solution having a concentration of at least 4 molarwhich reacts with the clay to form pile like intrusions in the claydeposit to anchor the deposit and thus provide stability to the deposit.Additional objects and advantages of the present invention will becomeapparent from reading the following detailed description in view of theaccompanying drawings which are made a part of this specification.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a clay containing earth formationillustrating in schematic form the preferred apparatus for admixing, inaccordance with the present invention, hydroxy-aluminum solution withclay in situ in the formation to thereby form a stabilizing pile in theformation.

FIG. 2 is an enlarged schematic view of a portion of the apparatus ofFIG. 1 and aids in providing a better understanding of the presentinvention.

FIG. 3 is a schematic plan view of an example layout of piles formed inaccordance with the present invention useful in stabilizing a clay soilformation under a roadbed.

FIG. 4 is a sectional view taken at line 4--4 of FIG. 3.

FIG. 5 is a schematic plan view of an example layout of piles formed inaccordance with the present invention useful in stabilizing a clay soilformation under a foundation of a building or the like.

FIG. 6 is a sectional view taken at line 6--6 of FIG. 5.

FIG. 7 is a schematic sectional view of test apparatus utilized inlaboratory demonstrations of diffusion effects when utilizing the methodof the present invention; and

FIGS. 8-14 are graphs showing plots of experimental data useful inunderstanding the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to stabilizing clay soil by admixingwith at least portions of such soil an effective amount ofhydroxy-aluminum solution having a concentration of at least 4 molar. Inpreferred form a plurality of pile-like deposits are formed in situ inthe clay soil deposit by admixing with wet clay at least 5 ml ofhydroxy-aluminum solution having a concentration of at least 4 molar per100 grams of clay soil wet weight. Best results appear to be obtainedwhen the hydroxy-aluminum solution concentration is greater than sixmolar. At least 5 ml of such solution per 100 grams clay soil wet weightis used. For different clays the optimum concentration ofhydroxy-aluminum may, of course, vary. Optimum concentration for a givenclay may be determined by simple laboratory tests as herein described.

Hydroxy-aluminum, useful in accordance with the present invention, has ahydroxyl to aluminum ratio of at least 2.0. At low pressure, hydroxyl toaluminum ratios of less than 2.2 tend to be so acidic that carbonatescontained in the clay soil turn to carbon dioxide which causes bubblesthat are undesired in the present invention. Therefore, in carbonatecontaining soils it is preferred to use hydroxy-aluminum having ahydroxyl to aluminum ratio of 2.5 in the present invention.

Thus, hydroxy-aluminum, useful in the present invention, has the generalformula Al(OH)_(n) X_(3-n) where n has a value of at least 2.0 andpreferably 2.5 to 2.7 and x is an anion selected from the groupconsisting of chloride, bromide, iodide, nitrate, sulfate and acetate.The hydroxy-aluminum solutions used in accordance with the presentinvention are aqueous solutions. Hydroxy-aluminum is a commerciallyavailable chemical and can be obtained, for example, from ReheisChemical Company of Berkeley Heights, N.J. or HoechstAktiengesellschaft, Frankfurt am Main, West Germany.

In accordance with the present invention, the concentration of thehydroxy-aluminum solution should be at least 4 molar. Best results areobtained when the concentration of the hydroxy-aluminum is 6 molar orgreater. Although at least one manufacturer indicates that a 6.2 molarsolution of hydroxy-aluminum is saturated, it has been found that muchmore concentrated solutions can be formed and used in accordance withthe present invention. Thus, concentrations of hydroxy-aluminum solutionof 9 to 10 molar are useful and desirable in accordance with the presentinvention. The highly concentrated solutions will gel more rapidly thanthe lower, i.e. 6.2 molar solutions which are very stable and have along shelf life. However, the more concentrated solutions, i.e. 7 to 10molar, may be prepared in the field and have sufficient life beforegelling to permit admixing with the clay to give beneficial results. Thetime at which a given hydroxy-aluminum solution will gel depends both onconcentration and temperature.

Thus, the higher the temperature and the higher the concentration, theshorter the gel time will be. A 9 molar solution of hydroxy-aluminum wasprepared and remained in solution at 74° F. for at least four hours. Itwas then left overnight and when observed sixteen hours later hadgelled. Simple experiments knowing temperature expected andclay-hydroxy-aluminum solution-clay mixing times can be done to permitoptimizing the molar concentration at the highest possible level.Concentration of the other chemical, for example potassium chloride,should preferably also be at least 4 molar to get the beneficial effectsof the invention.

In accordance with the present invention, hydroxy-aluminum solutionhaving a concentration of at least 4 molar, is thoroughly mixed with theclay soil to form pile-like extensions in the clay soil. Preferably, themixing is done in situ by a suitable mechanical means. In preferred formapparatus, such as schematically illustrated in FIGS. 1 and 2, may beused to mix the solution of the present invention with the normal claysoil. Referring to FIGS. 1 and 2, a clay soil deposit 10 is shown. Anauger-like device represented generally by the numeral 12, is shownpenetrating the clay deposit in bore 14 which will form the pile. Theauger 12 includes a bit 16 and a hollow drill stem 18. Means (not shown)are provided to rotate the auger 12 and to inject solution into and downdrill stem 18 for mixing with the clay soil 10 in bore 14.

FIG. 2 shows bit 16 in more detail. The bit is formed by a curvedcutting element 20 which when rotated mixing solution into clay soilinto which is advanced. A plurality of ports 22a, b, etc. are formed inthe collar 24 at the lower end of drill stem 18. Hydroxy-aluminumsolution is moved through the ports 22a, etc. and contacted with theclay as the auger is rotated and moved up or down into and out of theclay deposit. The solution mixes with the wet clay and reacts tostabilize the clay. The reaction is rapid but not immediate so thatmixing can occur both as the auger is driven down into the earth and asit is moved back up the bore. This is a particular advantage of thepresent invention over lime used heretofore. The reaction of lime withwet clay is so rapid that lime could only be injected into the clay asthe auger was being removed from the bore. Thus, the solution of thepresent invention can be more thoroughly mixed with the clay in situinsuring better results.

FIGS. 3 and 4 show an example of a practical application of the presentinvention. FIG. 3 is a schematic plan view of an example layout of pilesformed in accordance with the present invention useful in stabilizing aclay soil deposit under a roadbed. FIG. 4 is a sectional view taken atline 4--4 of FIG. 3.

A roadbed 40 is illustrated in FIGS. 3 and 4. The roadbed passes over anunstable clay deposit indicated generally as 42. In order to stabilizethe clay deposit 42 sufficiently to bear the stresses imposed by theroadbed 40 a series of pile-like structures indicated generally as 44,a, b, c, have been formed by mixing hydroxy-aluminum with the clay soil.Preferably, piles 44a, b, c are formed along the sides of the roadbed aswell as directly below the roadbed. Note that the piles not only serveto support the roadbed from below but also to assist in stabilizing thedeposit on both sides of the roadbed including the sloping side which issupported by piles 44c.

FIGS. 5 and 6 illustrate another example of a practical application ofthe present invention. FIG. 5 is a schematic plan view of an examplelayout of piles formed in accordance with the present invention usefulin stabilizing a clay soil formation located under a foundation of abuilding or the like. FIG. 6 is a sectional view taken at line 6--6 ofFIG. 5.

A building foundation is schematically shown in FIGS. 5 and 6 and isindicated by the numeral 50. A clay soil deposit 52 is located below thefoundation 50. A plurality of piles indicated by the numerals 56a, b, c,have been formed below, inside and outside of the foundation 50 tostabilize the clay deposit.

A series of laboratory demonstrations involving stabilizing clay wereconducted utilizing the hydroxy-aluminum solution of the presentinvention as well as other chemicals. These demonstrations will now bedescribed in detail with reference to FIGS. 7-14. FIG. 7 is a schematicsectional view of test apparatus utilized in laboratory demonstrationsof diffusion effects when utilizing the method of the present inventionand FIGS. 8-14 are graphs showing plots of experimental data useful inunderstanding the present invention.

Initially, two Norwegian clays were subjected to tests. These were aNorwegian quick clay and a marine salt clay. Almost all the presentdemonstration work was done on the Norwegian quick clay. Table 1 belowsets out the properties of the two clays.

                  TABLE I                                                         ______________________________________                                        PROPERTIES OF THE NORWEGIAN QUICK                                             CLAY AND MARINE SALT CLAY                                                     ______________________________________                                                          Clay Type                                                                       quick      salt                                           ______________________________________                                        Water Content (1% of dry weight -                                             Measured on the original clay                                                 as an average value for each tube)                                                                35.0-38.3  52                                             Shear Strength (kPa - Measured by                                             the falling cone method)                                                                           7-10      7.0                                            Porewater Chemistry                                                           pH                  7.9-8.2    8.0                                            Na (ppm)            150-300    --                                             K (ppm)             10-20      --                                             Ca (ppm)            10-40      --                                             Mg (ppm)             3-20      --                                             Conductive power    6.4 Ohms   --                                             CaCO.sub.3          1.4%       --                                             Organic carbon      0.6%       --                                             Salt content (expressed as N.sub.2 Cl)                                                            0.4 g NaCl/1                                                                             20 g                                                                          NaCl/1                                         Grain size          sand  1%    1%                                                                silt 57%   64%                                                                Clay 42%   35%                                            ______________________________________                                        Mineralogy  (clay)       (silt)                                               ______________________________________                                        Illite/Musc.                                                                              65%          30%       --                                         Chlorite    30%          10-15%    --                                         Quartz      0-5%         20%       --                                         K--feldspar              15-20%    --                                         Plagioclase  5%          15-20%    --                                         ______________________________________                                    

Aluminum-hydroxy chloride Al(OH)₂.5 Cl₀.5 (further noted ashydroxy-aluminum) has a stabilizing effect on Norwegian quick clay. Thequick clay, which is very soft in natural state, is liquid whenremoulded. After addition of hydroxy-aluminum the admixture will besolid at first, then soften somewhat with more silty properties. Withinminutes the mixture will polymerize and after a few days it will be ahard clay. The addition of lime used heretofore in the prior art has asomewhat similar effect. However, the difference betweenhydroxy-aluminum of the present invention and lime as stabilizing agentslies in how they act upon the surrounding undisturbed quick clay.Hydroxy-aluminum has a stabilizing effect some centimeters into theundisturbed clay with a firmness of about one-tenth of the admixture. Onthe other hand, lime has very small effects on the undisturbed clay.Compared with KCl which has also used alone heretofore, hydroxy-aluminumhas a much higher firmness in the mixture, but KCl diffuses much fasterinto the undisturbed quick clay and stabilizes the ground to some extentmany centimeters from the mixture. It has been found that a combinationof OH-Al and KCl takes care of the best properties of both stabilizingagents and give a hard core with a soft to medium undisturbed clay. As aresult of attracting water the firmness of the hydroxy-aluminum willdecrease somewhat to about one-third within a couple of months, buttotally this effect has little influence on the beneficial effect of thepresent invention.

In general, the laboratory demonstrations were divided into two parts.One part was concerned with determination of the optimum mixing ratio(Series A1) and the time dependency (Series A2) of dry hydroxy-aluminumand hydroxy-aluminum solution. The second part examined diffusioneffects from a stabilized clay into an undisturbed clay. Liquid andsolid hydroxy-aluminum as the only stabilizing agent are marked asSeries B1 and Series B2 respectively. Mixed with KCl they are markedSeries C1 and C2 and with methanol D1 and D2.

The demonstrations of part one show the superiority of utilizing dryhydroxy-aluminum over hydroxy-aluminum solution. However, it isrecognized that hydroxy-aluminum solution does provide substantialbeneficial effects. Table II sets out the concentrations ofhydroxy-aluminum used in the A1 series. In this regard note that the A1refers to the particular series; the next number refers to the number ofdays passed before sampling and the latter indicates the segment numbercounting from the top where the test was made.

                  TABLE II                                                        ______________________________________                                        In Series A1, with concentration variations, the following                    mixing ratio was used:                                                                  ml 6.2 M OH--Al or                                                            g OH--Al powder per 100 g                                                                       g OH--Al/100 g                                    Series No.                                                                              clay wet weight   clay dry weight                                   ______________________________________                                        A1-1a                                                                                   5 ml 6.2 M        3.62                                              A1-7a                                                                         A1-1b                                                                                   5 ml 0.62 M       0.362                                             A1-7b                                                                         A1-1c                                                                                   5 ml 0.062 M      0.0362                                            A1-7c                                                                         A1-1d                                                                                   5 ml 0.0062 M     0.00362                                           A1-7d                                                                         A1-7e     0.8               1.09                                              A1-7f     2.5               3.4                                               A1-7g     5                 6.8                                               A1-7h     10                13.6                                              A1-7i     15                20.4                                              ______________________________________                                    

In Series A2, with time variations, only 5 ml 6.2 M OH-Al/100 g clay wetweight was used with an experimental duration of 1h (hour), 1d (day),3d, 7d, 30d, and 100d. The same procedure was used for the salt marineclay illustrated as Series A3 in Table III.

The clay was mixed and put into a plastic beaker with cover. This wascovered with plastic films and put aside in a container with N₂ gas andstored at 7° C. Shear strength was measured on each sample. Some weresqueezed and the pore water measured with respect to pH and in a fewcases Ca, Mg, K, and Na by atomic absorption.

The results of a series of demonstrations conducted as described are setout in Table III below.

                                      TABLE III                                   __________________________________________________________________________    Results of the concentration dependent                                        experiments (A1), time dependent experiments (A2)                             and experiment with salt marine clay (A3) with dry                            hydroxy-aluminum and hydroxy-aluminum solution                                          Shear Strength                                                                           Water  Pore Water                                        Duration  After the Experiment                                                                     Content                                                                              Composition (ppm)                                 Code (days)                                                                             Undisturbed (kPa)                                                                        (%)  pH                                                                              Ca Mg K  Na                                       __________________________________________________________________________    A1-00                                                                              0    9.8        36.0 7.9                                                                             10.4                                                                             4.0                                                                               13                                                                              170                                      A1-1a                                                                              1    18.5            6.1                                                 A1-1b                                                                              1    5.0             7.2                                                 A1-1c                                                                              1    0.5             7.7                                                 A1-1d                                                                              1    <0.1            7.7                                                 A1-7a                                                                              7    50                                                                  A1-7b                                                                              7    6.5                                                                 A1-7c                                                                              7    1.2                                                                 A1-7d                                                                              7    <0.1                                                                A1-7e                                                                              7    39                                                                  A1-7f                                                                              7    70                                                                  A1-7g                                                                              7    145             6.9                                                                             6900                                                                             900                                                                              370                                                                              920                                      A1-7h                                                                              7    240                                                                 A1-7i                                                                              7    >375                                                                A2-01                                                                              1h   25                                                                  A2-1 1    18.5            6.1                                                 A2-3 3    61                4880                                                                             610                                                                              140                                                                              660                                      A2-7 7    50                                                                  A2-30                                                                              30                   6.7                                                                             6950                                                                             740                                                                              230                                                                              890                                      A2-100                                                                             104  60              6.7                                                 A2-7*                                                                              7    63              6.0                                                                             6670                                                                             720                                                                              170                                                                              790                                      A2-30*                                                                             28   75                                                                  A2-100*                                                                            102  78              7.5                                                 A3-00                                                                              0    7.0        52.2                                                     A3-01                                                                              1h   0.6                                                                 A3-1 1    0.6                                                                 A3-3 3    0.6                                                                 A3-7 7    0.8                                                                 A3-30                                                                              30   2.4                                                                 A3-100                                                                             100  3.8                                                                 A3-7f                                                                              7    1.9             8.0                                                                              260                                                                             680                                                                              240                                                                              6300                                     __________________________________________________________________________

The results shown in Table III show that results obtained with dryhydroxy-aluminum is superior to the beneficial results obtained withhydroxy-aluminum solution. The concentration of hydroxy-aluminumadmixture varied from 0-15% of clay wet weight (or 0-20% dry weight)(Series A1). The results presented in drawing in Table III show that theshear strength varies from that of liquid (<0.1 kPa) to a hard compactedclay (>375 kPa) when the admixture of hydroxy-aluminum rises. Acomparison of the liquid admixture with the dry admixture shows that theaddition of water together with hydroxy-aluminum decreases thestabilizing effect.

Small additions of dry hydroxy-aluminum (up to about 5%, i.e. 8% dryweight) turns the clay plastic immediately. While small addition ofhydroxy-aluminum gave plastic clay immediately, increased addition gaveat first a stiffer clay that within a minute of mixing turns looser.Then it got a silty character and changes slowly into a harder clay. Ifthe solid hydroxy-aluminum is not sufficiently mixed, it will attractwater and make a brittle gel.

Clay and hydroxy-aluminum solution were mixed at the standard ratio of 5ml of 6.2 M OH-Al to 100 g of clay wet weight and put aside for 1h(hour), 1d (day), 3d, 7d, 30d, and 100d. Shear strength tests werecarried out and the results are given in drawing in Table III. Testsmarked with * are carried out later than the others on perhaps lessoxidized clay. It is noteworthy that the shear strength is raised abovethat of the undisturbed clay after only a few minutes.

Salt marine clay and OH-Al were mixed at standard ratio of 5 ml of 6.2 MOH-Al to 100 g of clay (wet weight) and put aside for 1h (hour), 1d(day), 3d, 7d, 30d, and 100 days. Shear strength was measured and theresults are presented in drawing in Table III. Because of the very highwater content in the clay, additional water from liquid OH-Al made theclay liquid. Within 100 days the remoulded salt marine clay neverreached the original shear strength. The results will obviously bebetter with dry hydroxy-aluminum in this case.

The part two demonstrations to illustrate diffusion effects from thestabilized clay will now be discussed in detail. The diffusionexperiments there utilized small brass cylinders 35 mm in diameter withvarying height as schematically illustrated in FIG. 7. The cylinderswere sealed in the bottom and the uppermost 5 cm above the top of theundisturbed quick clay were filled with the mixture. As indicated inTable IV below, in the indicated series the remoulded clay mixturecomprised:

                  TABLE IV                                                        ______________________________________                                        B1   5 ml 6.2 M OH--Al/100 g clay wet weight                                  B2   15 g OH--Al powder/100 g clay wet weight                                 C1   5 ml 6.2 M OH--Al + 9.5 g solid KCl/100 g clay wet                            weight                                                                   C2   15 g OH--Al powder + 9.5 g solid KCl/100 g clay wet                           weight                                                                   D1   5 ml 6.2 M OH--Al + 5 ml methanol/100 g clay wet                              weight                                                                   D2   15 g OH--Al powder + 5 ml methanol/100 g clay wet                             weight                                                                   ______________________________________                                    

The samples were sealed with plastic and put aside for 7d (days), 30d,and 100d in an N₂ filled container at 7° C. The consistency of themixtures caused only small problems. The remoulded clay in the B serieswas liquid, in the C series dry and plastic, and in the D series wet andplastic.

After storage the clay columns were pushed out and shear strengthmeasured. Afterwards the clay was cut into slices 2.5 cm each. Out ofeach slice, one part was measured with regard to water content, andanother part squeezed and measured with regard to pH and analyzed forCa, Mg, K, and Na in pore water by atomic absorption.

Tables V through IX below and FIGS. 8-14 illustrate the results of thesedemonstrations.

In these tables the series number is followed by a specimen numberindicating the experimental duration in days. A third number indicatesthe segment number, counted from the top of the cylinder downwards. Forinstance, C2-30-8, where C-2 denotes solid OH-Al mixed with KCl, 30denotes 30 days' duration and 3 denotes the third segment from the top.

Each segment is measured with regard to shear strength. The methodapplied is the falling cone method, where a sharp cone penetrates by itsown gravity into the clay. Millimeters of penetration are transformedinto kPa (kN/m²) by a standard curve. Other measured parameters werewater content (in % of dry weight), pH, and Ca-, Mg, K-, and Na-contentof the squeezed pore water. The elements were measured by atomicabsorption with a precision that may reach an uncertainty of ±60% insome of the results. As a reference for the experiments, the naturalquick clay was analyzed with regard to mineralogy, grain sizedistribution, cation exchange capacity, inorganic and organic carbon andsalt content.

                                      TABLE V                                     __________________________________________________________________________    Results of the Diffusion Experiments with Hydroxy-aluminum                    OH--Al Solution (B1) and Dry Hydroxy-aluminum (B2)                                      Shear Strength                                                                           Water  Pore Water                                        Duration  After the Experiment                                                                     Content                                                                              Composition (ppm)                                 Code (days)                                                                             Undisturbed (kPa)                                                                        (%)  pH                                                                              Ca Mg K  Na                                       __________________________________________________________________________    B1-7-1                                                                              7   63         44.3 7.6                                                 B1-7-2    63         43.1 6.7                                                                             5000                                                                             1410                                                                             150                                                                              750                                      B1-7-3    14         31.6 7.3                                                                             610                                                                              270                                                                              64 610                                      B1-7-4    11.7       34.8   200                                                                              89 44 440                                      B1-7-5               36.6                                                     B1-7-6    9.2        36.8                                                     B1-30-1                                                                             28  73         44.5                                                     B1-30-2   63         47.9 7.1                                                                             5010                                                                             500                                                                              5700                                                                             510                                      B1-30-3   22         33.2   3520                                                                             530                                                                              2570                                                                             610                                      B1-30-4   23         36.0 7.9                                                                             660                                                                              270                                                                              330                                                                              500                                      B1-30-5   21         37.0                                                     B1-30-6   15         37.8                                                     B1-100-1                                                                           100  52         44.3                                                     B1-100-2  73         44.5 7.8                                                                             4020                                                                             450                                                                              110                                                                              720                                      B1-100-3  14         33.2 7.4                                                                             3600                                                                             480                                                                              88 960                                      B1-100-4  11         36.3 8.3                                                                             2260                                                                             460                                                                              99 610                                      B1-100-5  10         37.2 8.3                                                                             1480                                                                             390                                                                              75 670                                      B1-100-6  15         38.2 8.3                                                                             780                                                                              400                                                                              86 710                                      B2-7-1                                                                              7   310        33.9                                                     B2-7-2    310        40.7                                                     B2-7-3    27         34.2   3720                                                                             610                                                                              110                                                                              680                                      B2-7-4    25         35.8 7.3                                                                             370                                                                              98 27 440                                      B2-7-5    15         36.3 7.6                                                                             31 5.2                                                                              13 200                                      B2-7-6    24         34.3 7.8                                                                             65 6.2                                                                              18 200                                      B2-30-1                                                                             30  140        40.4                                                     B2-30-2   98         43.5                                                     B2-30-3   25         36.9 6.5                                                                             3550                                                                             660                                                                              270                                                                              810                                      B2-30-4   31         38.0 7.9                                                                             760                                                                              350                                                                              110                                                                              750                                      B2-30-5   27         35.7 8.1                                                                             160                                                                              140                                                                              60 620                                      B2-30-6   23         35.0 8.5                                                                             28 21 77 450                                      B2-100-1                                                                           100  90         44.6                                                     B2-100-2  125        42.7                                                     B2-100-3  40         35.6 7.2                                                                             6120                                                                             870                                                                              200                                                                              1210                                     B2-100-4  52         34.3 7.2                                                                             2200                                                                             420                                                                              100                                                                              850                                      B2-100-5  32         33.1   1850                                                                             580                                                                              200                                                                              950                                      B2-100-6  20         33.5   1150                                                                             530                                                                              220                                                                              1040                                     __________________________________________________________________________

                                      TABLE VI                                    __________________________________________________________________________    Results of the Diffusion Experiments With                                     Hydroxy-aluminum Solution and Potassium Chloride                                        Shear Strength                                                                           Water  Pore Water                                        Duration  After the Experiment                                                                     Content                                                                              Composition (ppm)                                 Code (days)                                                                             Undisturbed (kPa)                                                                        (%)  pH                                                                              Ca Mg K   Na                                      __________________________________________________________________________    C1-7-1                                                                              7   26         55.4                                                     C1-7-2    31         52.0 6.0                                                                             4260                                                                             540                                                                              64700                                                                             600                                     C1-7-3    26         34.4 7.0                                                                             2390                                                                             560                                                                              39500                                                                             620                                     C1-7-4    15         33.3 8.2                                                                             770                                                                              500                                                                              12000                                                                             780                                     C1-7-5    10         36.0 8.6                                                                             250                                                                              170                                                                              960 520                                     C1-7-6    9.5        36.8   63 121                                                                              580 210                                     C1-30-1                                                                            30   72         42.9 6.5                                                                             5080                                                                             580                                                                              58500                                                                             740                                     C1-30-2   55         43.4                                                     C1-30-3   53         32.7                                                     C1-30-4   33         35.5 6.8                                                                             1470                                                                             560                                                                              21800                                                                             820                                     C1-30-5   31         36.5   710                                                                              470                                                                              7740                                                                              570                                     C1-30-6   32         36.7 6.7                                                                             520                                                                              370                                                                              1610                                                                              590                                     C1-30-7   27         36.5 6.8                                                                             270                                                                              180                                                                              450 520                                     C1-30-8   16         37.1 7.1                                                                             74 34 48  370                                     C1-30-9   15         35.2                                                     C1-30-10  3.0        38.1 7.8                                                                             45 8.0                                                                              40  240                                     __________________________________________________________________________

                                      TABLE VII                                   __________________________________________________________________________    Results of the Diffusion Experiments With                                     Dry Hydroxy-aluminum and Potassium Chloride                                              Shear Strength                                                                           Water  Pore Water                                       Duration   After the Experiment                                                                     Content                                                                              Composition (ppm)                                Code  (days)                                                                             Undisturbed (kPa)                                                                        (%)  pH                                                                              Ca Mg K   Na                                     __________________________________________________________________________    C2-7-1                                                                               7   280        32.0                                                    C2-7-2     >375       36.1                                                    C2-7-3     33         33.7 7.3                                                                             2880                                                                             670                                                                              32700                                                                             820                                    C2-7-4     31         35.6 8.0                                                                             570                                                                              420                                                                              6800                                                                              630                                    C2-7-5     18         37.3 7.6                                                                             105                                                                              64 180 380                                    C2-7-6     11         34.9 7.8                                                                             37 5.3                                                                              21  180                                    C2-30-1                                                                              30  310        37.9                                                    C2-30-2    375        38.6                                                    C2-30-3    30         34.8 7.6                                                                             4160                                                                             800                                                                              52000                                                                             960                                    C2-30-4    36         34.4 7.7                                                                             1540                                                                             630                                                                              26400                                                                             880                                    C2-30-5    30         36.9                                                    C2-30-6    27         40.5 8.4                                                                             450                                                                              380                                                                              3840                                                                              710                                    C2-30-7    31         34.4                                                    C2-30-8    12         38.1 8.3                                                                             38 15 39  340                                    C2-30-9    11         35.8                                                    C2-30-10   15              7.5                                                                             19 5.1                                                                              20  270                                    C2-100-1                                                                            100  95         44.4                                                    C2-100-2   240        45.0                                                    C2-100-3   29         33.6 7.6                                                                             3620                                                                             890                                                                              35500                                                                             1210                                   C2-100-4   39         37.3                                                    C2-100-5   39         38.4 8.0                                                                             1700                                                                             660                                                                              20200                                                                             1000                                   C2-100-6   42         34.8                                                    C2-100-7   42         39.9 8.2                                                                             660                                                                              470                                                                              5780                                                                              750                                    C2-100-8   24         34.9                                                    C2-100-9   23         37.3 8.3                                                                             360                                                                              300                                                                              1240                                                                              620                                    C2-100-10  23         36.0                                                    C2-100-11  19         36.9 8.3                                                                             54 36 79  440                                    C2-100-12  14         37.2                                                    C2-100-13  11         38.2 8.3                                                                             25 6.8                                                                              53  280                                    C2-100-14  8.3        33.8 8.3                                                                             150                                                                              9.0                                                                              69  350                                    __________________________________________________________________________

                                      TABLE VIII                                  __________________________________________________________________________    Results of the Diffusion Experiments with                                     Hydroxy-aluminum Solution and Methanol                                                  Shear Strength                                                                           Water  Pore Water                                        Duration  After the Experiment                                                                     Content                                                                              Composition (ppm)                                 Code (days)                                                                             Undisturbed (kPa)                                                                        (%)  pH                                                                              Ca Mg K  Na                                       __________________________________________________________________________    D1-7-1                                                                              7   26         55.4                                                     D1-7-2    31         52.0 6.0                                                                             4400                                                                             500                                                                              93 440                                      D1-7-3    26         34.3 7.0                                                                             1480                                                                             300                                                                              64 460                                      D1-7-4    15         33.3 8.2                                                                             150                                                                              56 28 360                                      D1-7-5    10         36.0 8.6                                                                             58 13 16 190                                      D1-7-6    9.5        36.8                                                     D1-30-1                                                                             29  31         56.7                                                     D1-30-2   31         49.6 6.9                                                                             3530                                                                             430                                                                              82 390                                      D1-30-3   22         51.7 7.7                                                                             2130                                                                             380                                                                              61 430                                      D1-30-4   21         38.6 8.0                                                                             840                                                                              280                                                                              47 440                                      D1-30-5   19         36.9                                                     D1-30-6   9.1        37.4 8.3                                                                             62 12 15 280                                      D1-30-7   10         36.7                                                     D1-30-8   7.6        37.6 8.1                                                                             17 4.5                                                                              14 170                                      D1-30-9   7.8        35.9                                                     D1-30-10  9.2        38.8 8.2                                                                             12 4.0                                                                              13 170                                      D1-100-1                                                                           105  <0.1       89.9                                                     D1-100-2  39         52.0 6.1                                                                             2850                                                                             420                                                                              150                                                                              660                                      D1-100-3  15         38.4 6.5                                                                             2360                                                                             420                                                                              130                                                                              710                                      D1-100-4  18         39.1 7.0                                                                             1370                                                                             370                                                                              94 760                                      D1-100-5  15         39.4 7.3                                                                             970                                                                              330                                                                              106                                                                              810                                      D1-100-6  11         35.9 7.5                                                                             310                                                                              220                                                                              83 770                                      __________________________________________________________________________

                                      TABLE IX                                    __________________________________________________________________________    Results of the Diffusion Experiments with                                     Solid Dry Hydroxy-aluminum and Methanol                                                 Shear Strength                                                                           Water  Pore Water                                        Duration  After the Experiment                                                                     Content                                                                              Composition (ppm)                                 Code (days)                                                                             Undisturbed (kPa)                                                                        (%)  pH                                                                              Ca Mg K  Na                                       __________________________________________________________________________    D2-7-1                                                                              7   125        42.7                                                     D2-7-2    90         49.8                                                     D2-7-3    41         35.4 7.9                                                                             1630                                                                             380                                                                              52 600                                      D2-7-4    24         36.0 8.3                                                                             230                                                                              110                                                                              38 470                                      D2-7-5    13         37.0 8.4                                                                             25 5.9                                                                              14 170                                      D2-7-6    7          34.9 8.5                                                                             22 5.6                                                                              45 150                                      D2-30-1                                                                             30  48         49.7                                                     D2-30-2   27         55.9                                                     D2-30-3   33         34.7 7.4                                                                             4200                                                                             540                                                                              102                                                                              720                                      D2-30-4   35         35.1 8.2                                                                             930                                                                              290                                                                              63 690                                      D2-30-5   27         36.3                                                     D2-30-6   18         39.4 8.3                                                                             32 14 29 340                                      D2-30-7   14         34.0                                                     D2-30-8              34.8 8.3                                                                             43 5.8                                                                              25 190                                      D2-30-9   7.1        49.0                                                     D2-30-10  10         35.3 8.5                                                                             40 3  15 180                                      D2-100-1                                                                           102  <0.1       51.5                                                     D2-100-2  <0.1       33.5                                                     D2-100-3             49.0   4190                                                                             710                                                                              200                                                                              630                                      D2-100-4             34.2   2250                                                                             550                                                                              160                                                                              740                                      D2-100-5             34.0   1350                                                                             500                                                                              170                                                                              860                                      D2-100-6             33.0   1530                                                                             530                                                                              180                                                                              960                                      __________________________________________________________________________

In the demonstrations of part 2 and as shown in Tables V-IX above andFIGS. 8-14, cylinders of undisturbed quick clay were used. The length ofthe cylinders varied from 10 to 30 cm. Some of them contained siltylayers, which caused varying shear strength and water content, and mostprobably also somewhat affected the diffusion.

The inhomogeneity of the cylinders may cause disturbances both when theclay is pushed into the cylinders and out of them. Sometimes thedisturbances caused drainage of water, that was gathered at the bottom.Oxidation of the clay was depressed because the cylinders were stored inN₂ atmosphere at 7° C.

As shown in FIG. 7 the remoulded clay stabilized with eitherhydroxy-aluminum and KCl or hydroxy-aluminum and methanol orhydroxy-aluminum alone was placed at the top of the cylinders. Then thecylinders were sealed with several plastic layers and put aside for 7,30 or 100 days. At the end of each run the clay was pushed out and thevarious parameters measured down the cylinder.

When remoulded and mixed with (6.2 M) hydroxy-aluminum solution, theclay turns stiff (60 kPa) and remains stiff (50-80 kPa) throughout thetesting period. Table V and TAble VI, show rather low shear strengthvalues in the undisturbed clays caused by diffusion. The efficiency andthe penetration of the stabilizing effect in the undisturbed clay arenot clear.

The water content shows that the hydroxy-aluminum admixture draws thewater out of the undisturbed clay. This effect is also observed in allthe other experiments. Another parameter with much the same developmentin all experiments is the pH value. Hydroxy-aluminum has an acidicreaction, which penetrates to some extent down the column, but will beneutralized by time. The pore water chemistry is much the same in thethree experiments. There are two exceptions: Extremely high potassiumrelease in B1-30 series and high magnesium content in B1-7 series.

Remoulding of the quick clay with hydroxy-aluminum apparently releases asubstantial amount of cations to the pore fluid. For instance thepotassium concentration increases by a factor of nearly 10, magnesium byabout 100 and calcium by more than 200. The resulting concentrationdifference between the remoulded and the undisturbed clay, subsequentlydrives the diffusion of these cations into the undisturbed clay.

Dry hydroxy-aluminum admixture gives much better geotechnical resultscompared to the beneficial results of hydroxy-aluminum solutionadmixture in this clay. The remoulded clay immediately gets a highershear strength which with time reduces to about 1/3 of the originalshear strength value as shown in Tables V, VI, VII and VIII. Thestabilizing effect with time on the undisturbed clay are less ambiguouswith dry hydroxy-aluminum than with hydroxy-aluminum solution. Thepenetration series into the original clay develops a medium strength(25-50 kPa) 4-9 cm down to the column during the test period.

Water content measurements confirm the already predicted osmotic effectof hydroxy-aluminum. The remoulded clay contains 30% more water than theundisturbed clay after 100 days. pH-measurements als confirm the acidreaction of hydroxy-aluminum. The difference may be at least 2 pH-unitsfrom the disturbed to the undisturbed clay. The pore water chemistryexhibits much the same trend as described before. The B2-100 series,however, shows for unknown reason higher release of Ca, Mg, and Na.Compared with hydroxy-aluminum solution dry hydroxy-aluminum releases Kand Mg to the same extent (factor of 10 and 100), but Ca to a somewhatlesser extent; a factor of 100-200.

As shown in Table VI, admixing (6.2 M) hydroxy-aluminum solution andsolid KCl gives a stiff remoulded clay with a shear strength of 50-80kpa which is independent of experimental duration. The diffusion ofspecies downwards in the undisturbed clay causes a medium stiff clay(25-50 kPa) to a depth of 6 cm (B1-7) and 11 cm the increased shearstrength in the undisturbed clay is most probably caused by thediffusion of potassium ions.

Water content measurements indicate that some water drainage has takenplace in the C1-7 series. Still it is possible to notice the osmoticeffect of hydroxy-aluminum as indicated above. pH-measurements show agreat difference between stabilized and undisturbed clay (at least 2.5pH-units) at the beginning of the experiments. With time, the acid (H+)penetrates down the column and is slowly neutralized. The pore waterchemistry has no different trends compared with already describedexperiments, except for the great addition of potassium. One dimensionaldiffusion constants have been estimated for K in both experiments in theC1 series. Approximate values are 6×10⁻⁶ cm² sec⁻¹ for 7 days experimentand 3×10⁻⁶ cm² sec⁻¹ for 30 days' experiment. The values are approximatebecause of no exact information of the reservoir concentration, or ofthe constancy of the reservoir concentration, the inhomogeneity of theclay and no chemical reactions or physical changes of the clay have beentaken into account. The contents of Mg and Ca in the pore water are muchthe same as in series B1.

Table VII shows the results of dry hydroxy-aluminum and potassiumchloride as stabilizing chemicals. This admixture gives a hard remouldedclay with an initial shear strength of 300-400 kPa which decreasesduring the test period to 100-200 kPa. The diffusion of species downwardin the undisturbed clay causes a medium stiff clay (25-50 kPa) to adepth of 5 cm (C2-7), 10 cm (C2-10), and 20 cm (C2-100). It isnoteworthy that the maximum shear strength in the undisturbed clayincreases a little during the experimental period. As in series C1,potassium diffusion is the main reason for this increased shearstrength.

Water content measurements show the same development as describedearlier. The water content of the stabilized mixture increases withabout 30% from 7 to 100 days. However, the decreased water content ofthe undisturbed clay is not explicitly expressed in the measurements ofthe undisturbed clay.

pH-measurements are available from only the undisturbed clay and showonly a slight increase down the column. This trend is like thosedescribed before.

There are no considerable differences between these and the previousdescribed pore water chemistry results. The one dimensional diffusioncoefficients estimated for K in the three experiments were: 4×10⁻⁶ cm²sec⁻¹ (C2-7), 4×10⁻⁶ cm² sec⁻¹ (C2-30), and 3×10⁻⁶ cm² sec⁻¹ (C2-100).The content of Ca and Mg in pore water are much the same as B2 series.

Demonstrations were conducted with hydroxy-aluminum solution containingmethanol. The results are given in Table VIII. This admixture gives arather soft remoulded clay which partly turns liquid during the testperiod (D1-100). The stabilizing effect of diffusing substances seemsrather small. Only the uppermost 1 cm of the undisturbed clay has shearstrength above 25 kPa in the beginning of the period, while someadditional centimeters give values between 15 and 25 kPa. These resultsare not far from the B1 series which indicates that any positive effectof added methanol must be insignificant.

Water content measurements are ambiguous in showing the water attractingtendencies, probably because of additional liquid content in methanol.The pH-measurements show clearly a pH-gradient with H+ diffusion fromthe source down the column. The pore water chemistry values are verysimilar to those previously described.

Demonstrations were also conducted with dry hydroxy-aluminum withmethanol as a stabilizing agent. The results are shown in Table IX. Thisadmixture gives a stiff to very stiff (approximately 100 kPa) remouldedclay mixture within 7 days. After 30 days however, the shear strengthhas dropped to that of a medium clay (about 40 kPa). Unfortunately theD2-100 series was destroyed and no shear strength results were obtainedfrom it. It is noteworthy that the upper 3 centimeters of the remouldedclay was turned liquid, the next centimeters very soft and the lastcentimeters stiff or very stiff. In the undisturbed clay shear strengthincreased to that of a medium clay (25-50 kPa) 4 cm down the column in 7days and 7 cm in 30 days. It was impossible to estimate the penetrationin the D2-100 series.

Water content measurements show great irregularities, but it is obviousthat the admixture attracts water and even makes the remoulded clayliquid. The pH-gradients have the same trends as described before. Thepore water chemistry also shows the same concentrations and trends as inthe other series with dry hydroxy-aluminum. Specially for D2 series,however, is the penetration of species into the undisturbed claysomewhat slower.

FIG. 8 shows a comparison of hydroxy-aluminum solution alone and withvarious additives after 7 days. The hydroxy-aluminum solution admixturegives a stiff clay mixture (65 kPa) after 7 days. The addition of KClcauses no changes, but the addition of methanol reduces the shearstrength to about 30 kPa probably due to increased liquid addition. Inthe undisturbed clay the hydroxy-aluminum solution causes a very smallincrease in shear strength and only to a depth of a few centimeters. Theaddition of methanol gives a little more efficient increase of the shearstrength in the same few upper centimeters. The addition of KClincreases shear strength to a greater depth than the two others. Thereason is most probably the addition of potassium, but some of the shearstrength increase could have been caused by the released diffusingspecies like Ca and Mg.

FIG. 9 shows a comparison of dry hydroxy-aluminum alone and with variousadditives after 7 days. Dry hydroxy-aluminum admixture increases theshear strength of the remoulded clay to about 300 kPa (hard clay).Admixture of dry hydroxy-aluminum and KCl gives about the same shearstrength, while addition of hydroxy-aluminum together with methanol onlyresults in a shear strength of 100 kPa. The lower strength obtained withmethanol, is obviously caused by the liquid addition.

The increase of shear strength in the undisturbed clay are much the samein all three experiments with a medium stiff clay (25-50 kPa) down to4-5 cm. The differences between the series with and without KCl are alsoshown by the pore water chemistry where Ca, Mg, and K almost everywhereare higher in the KCl addition experiment. Why the shear strength in theD2 series lies above all the other, may be caused either by theCa-concentration in the pore water or by the methanol content.

FIG. 10 shows a comparison of hydroxy-aluminum solution alone and withvarious additives after 30 days. Hydroxy-aluminum solution addition gaveshear strength of about 70 kPa in the remoulded clay (drawing 036),nearly the same as hydroxy-aluminum solution and KCl admixture (about 60kPa), while hydroxy-aluminum solution with methanol addition onlyreached 30 kPa.

In the undisturbed clay hydroxy-aluminum solution with or withoutmethanol addition follow each other to a great extent. They have astrength of about 20 kPa 7-8 cm down the column even if the pore waterchemistry of the series are not the same. Hydroxy-aluminum solution andKCl admixture is much more efficient than the other since it gives amedium stiff clay 11 cm down the column. Except for the first twocentimeters the pore water content of Ca, Mg, and of course K are muchgreater in the C1-30 series than in the others, and this may be thereason why the shear strength values are much higher.

FIG. 11 shows dry hydroxy-aluminum data after 30 days. Dryhydroxy-aluminum admixtures give greater spreading in the shear strengthvalues for different additions. Dry hydroxy-aluminum admixture givesabout 100 kPa in the remoulded clay (drawing 037) while hydroxy-aluminumand KCl additions are much more efficient with 300-400 kPa. On the otherhand hydroxy-aluminum and methanol admixture causes lower shearstrength: 30-60 kPa.

In the undisturbed clay the hydroxy-aluminum and methanol admixture aremost efficient the first 2 cm (about 35 kPa) just like the 7 daysseries. For the next 7 cm gives the hydroxy-aluminum and KCl admixturethe greatest shear strength (25-35 kPa). There is a greater differencebetween the shear strength of the different admixtures after 30 daysthan after 7 days. In this series (B2-30, C2-30, and D2-30) there is noobvious connection between shear strength in undisturbed clay and porewater chemistry like that described before.

FIGS. 12 and 13 show comparison of the different stabilizing agentsafter 100 days. Hydroxy-aluminum solution admixture gives a stiff clay(50-80 kPa) even after 100 days, while the hydroxy-aluminum solution andmethanol admixture gives varied values from that of a liquid (<0.1 kPa)in the uppermost 3 cm to 40 kPa in the lower 2 cm. The experiment withhydroxy-aluminum solution and KCl was not carried through.

The undisturbed clay are affected only to a small extent by themixtures. The shear strength scarcely exceed 15 kPa to a depth of about7 cm in hydroxy-aluminum solution and methanol admixture and only about1 cm with the hydroxy-aluminum solution alone. There is a decrease ofthe shear strength in the undisturbed clay from 7 and 30 daysexperiments with hydroxy-aluminum solution.

As shown in FIG. 13, dry hydroxy-aluminum addition to quick clay gives ashear strength that increases from 90 to about 400 kPa from the top tobottom of the remoulded clay. This result is not far from the additionof dry hydroxy-aluminum and KCl which varies within the same values. Theexperiment with dry hydroxy-aluminum with methanol was destroyed andshear strengths were not obtained. In this case the uppermost 3 cm werein a liquid state.

In the undisturbed clay the shear strength exceed that of 30 days seriesto some extent. With dry hydroxy-aluminum alone the shear strengthvaried from 20-50 kPa to a depth of 9 cm, 4 cm of this exceed 40 kPa. Onthe other hand, admixture of dry hydroxy-aluminum and KCl shows shearstrength between 25 and 50 kPa to a depth of 14 cm and higher than 20kPa for additional 7 cm. There is a relatively good correlation betweenshear strength and pore water content of Ca, Mg, and K.

FIG. 14 shows a comparison of solid dry hydroxy-aluminum alone; KCl; andCaO stabilization after 100 days. Comparison of shear strength in theremoulded clay shows that dry hydroxy-aluminum admixture reaches astiffness that exceeds that of CaO. This may be a coincidence becauseother mixing ratio and better tamping may increase the shear strength.KCl alone gives no stabilization effects.

In the undisturbed clay the stabilization effect is limited. Within 3 cmthe shear strength below the CaO-stabilized clay drops from 100 to 20kPa. With dry hydroxy-aluminum it drops from 50 to 20 kPa, 9 cm down thecolumn while KCl have 20-25 kPa to a depth of 19 cm. The increased shearstrength in the undisturbed clay is in CaO stabilization caused by thegreat water absorbing effect of lime. Hydroxy-aluminum has also asearlier described, a water attracting effect, but in this case theeffect goes deeper into the column, probably because of higher cationcontent. In the lime stabilization experiment, the water transportupwards is camouflaged by the chemical reaction CaO+H₂ O→Ca(OH)₂, whichbinds a large amount of water. KCl has probably no effect on the watercontent.

Hydroxy-aluminum solution of at least 4 molar concentration is apromising stabilizing agent. As a practical matter at least a mixingratio of at leat 5 ml of hydroxy-aluminum solution of at least 6 molarconcentration and preferably at the highest concentration which willremain in solution for mixing, i.e. 8 to 10 molar concentration, to 100grams of clay (wet weight) should be used.

From the above description it is evident that the present inventionprovides a method of stabilizing clay of said deposits by admixinghydroxy-aluminum solution of at least 4 molar concentration with theclay soil. Although only specific embodiments of the present inventionhave been described in detail, the invention is not limited thereto butis meant to include all embodiments coming within the scope of theappended claims.

What is claimed is:
 1. A method of stabilizing quick clay and salt claysoil comprising admixing the quick clay and salt clay soil with aneffective amount of hydroxy-aluminum solution having a concentration ofat least 4 molar.
 2. The method of claim 1 where said solution is at aconcentration of at least 6 molar.
 3. The method of claim 2 where atleast 5 ml of solution, per 100 grams clay soil wet weight is admixedwith said clay soil.
 4. The method of claim 1 where the concentration ofsaid solution is between 6 and 10 molar.
 5. The method of stabilizing aquick clay or salt clay containing soil deposit by forming a pluralityof pillars extending into said formation comprising the steps ofselecting the size of pillars to be formed, determining the wet weightof the clay within said pillars and admixing hydroxy-aluminum solutionof at least 4 molar concentration with said clay to form said pillars.6. The method of claim 5 where said solution has a concentration of atleast 6 molar.
 7. The method of claim 6 further characterized in thatsaid solution of hydroxy-aluminum is admixed with said clay soil in situin said deposit.
 8. The method of claim 5 where the concentration ofsaid solution is between 6 and 10 molar.